Pregnant women turning to pot for morning sickness, study finds

By Rachael Rettner

The researchers found that pregnant women with severe nausea and vomiting in their first trimester had nearly four times greater odds of using marijuana in pregnancy, compared with pregnant women who didn't experience morning sickness.  (iStock)

It's becoming more common for pregnant women to use pot in pregnancy, and a new study suggests one reason for the trend: Some pregnant women may be using marijuana to self-medicate symptoms of morning sickness.

The study, published today (Aug. 20) in the journal JAMA Internal Medicine, examined women's morning sickness symptoms and marijuana use.

The researchers found that pregnant women with severe nausea and vomiting in their first trimester had nearly four times greater odds of using marijuana in pregnancy, compared with pregnant women who didn't experience morning sickness. And women with mild nausea and vomiting in pregnancy had two times greater odds of using marijuana, compared with women who didn't have these symptoms.

The findings add to "a small but growing body of research suggesting that some pregnant women may use marijuana to self-medicate morning sickness," lead study author Kelly Young-Wolff, a research scientist at the Kaiser Permanente Division of Research in northern California, said in a statement.

Marijuana and morning sickness

In recent years, the percentage of pregnant women who report using marijuana has increased, from about 2.4 percent in 2002 to nearly 4 percent in 2014, according to a 2017 study. However, the reason behind the rise is unclear, and one hypothesis is that pregnant women are using marijuana to treat symptoms of morning sickness. However, few studies have looked at the link between marijuana use in pregnancy and symptoms of morning sickness.

In the new study, the researchers analyzed information from more than 220,000 pregnant women in northern California. These women filled out a survey about their substance use and provided urine samples in their first trimester for drug screening. The researchers also examined the participants' medical records, looking for diagnoses of mild or severe morning sickness.

Overall, 2.3 percent of women had diagnoses of severe morning sickness, 15.3 percent had diagnoses of mild morning sickness and the rest did not report symptoms of morning sickness.

Among the women with severe morning sickness, 11.3 percent used marijuana, compared with just 4.5 percent of women with no reported symptoms of morning sickness. Marijuana use was also higher among women who had mild morning sickness, with about 8.4 percent of those in this group using marijuana.

It's important to note that the study found only an association between marijuana use and symptoms of nausea and vomiting in pregnancy. Although the results suggest that pregnant women may be using the drug to self-medicate for these symptoms, the study cannot rule out other possible explanations for the findings. For example, doctors could be diagnosing nausea and vomiting in pregnancy more frequently in women who use marijuana, or marijuana may be contributing to symptoms of nausea and vomiting in pregnancy, the researchers said.

Still, the findings suggest that pregnant women with nausea and vomiting should be screened for marijuana use and educated about safe and effective treatments for morning sickness, the researchers said.

"We hope our study can help alert clinicians to the fact that women with nausea and vomiting in pregnancy are more likely to use marijuana," said senior study author Dr. Nancy Goler, an obstetrician/gynecologist at Kaiser Permanente in northern California. "Pregnant women need to be screened and given the information about the possible negative effects while also receiving medically recommended treatment options."

The health effects of using marijuana in pregnancy are unclear, and some studies suggest a link between marijuana use in pregnancy and problems in newborns, such as low birth weight and impaired neurological development. The American College of Obstetricians and Gynecologists recommends that pregnant women not use marijuana.

In future studies, the researchers hope to examine how pregnant women use marijuana — for example, by smoking it or consuming edibles. The scientists also want to study whether trends in marijuana use among pregnant women change when the drug is legalized.